The determination of the nature of diffuse liver diseases is important in determining patient management. At present, only invasive and limited noninvasive methods are available for reliable diagnosis. The purpose of this proposal is to demonstrate the feasibility of identification and differentiation of normal and diffusely diseased livers in vivo using noninvasive ultrasonic pulse echo methods. Specifically, this is achieved by measuring the nonlinear frequency dependent attenuation parameters of these tissues. Our preliminary studies show that it is possible to differentiate between normal and certain diffuse liver conditions based on the nonlinear attenuation parameters, which we have shown to be related to the basic absorption and scatterning properties of these tissues. The measurements will first be performed on a large number of in vitro liver samples. A reference archive of liver attenuation parameters and their respective pathologies will be collected. Thereafter, these tissue parameters will be measured in vivo using a computer based system. This instrument will be tested using tissue mimicking phantoms whose nonlinear attenuation parameters can be varied in a controlled way. This is necessary in order to experimentally determine the smallest measurable changes in these parameters. The in vivo attenuation values of the livers will be compared to the previously archived values obtained from the in vitro studies. A tentative identification of the disease will then be made. The nature of the disease will be independently verified. Thus, quantitative ultrasonic techniques developed here would be clinically useful for improved diagnosis.